/Engine/Source/Runtime/HeadMountedDisplay/Public/IXRInput.h
Passing touch events to HMD. If returns 'false' then touch will be handled by PlayerController; otherwise, touch won't be handled by the PlayerController.
virtual bool HandleInputTouch ( uint32 Handle, [ETouchType::Type](API\Runtime\InputCore\ETouchType__Type) Type, const FVector2D & TouchLocation, [FDateTime](API\Runtime\Core\Misc\FDateTime) DeviceTimestamp, uint32 TouchpadIndex )